Can someone please go over "the night before the camping trip". Via an electric extension cord, I wanted to plug my Bullet in the night before to get cool the fridge. But from what I remember, I can cool the fridge only from the propane tanks, for a few hours, and then via the AUTO button have it automatically switch over to the 120V. My confusion and fear is I don't want to empty my propane tanks overnight. Is this right? I believe the micro only works from the 120V. We want to load up all our food the night before in our fridge and have it ready to go the next morning or whenever we leave! Thanks Bullet Brothers!